(a) Field of the Invention
The present invention is related to an innovation characterized by integrating the advantage of a series-connected hybrid driving system and the advantage of a parallel-connected hybrid driving system; under normal loading condition, it enable an engine running with high speed and high power to drive a load, and specifically, in the condition of low-power, low-speed light-load driving, it drives the light load by means of its series-connected hybrid driving system with less power generating, under this operating mode, the electric storage device (E.S.D.) is isolated from system operation to reduce the capacity demand of E.S.D.
(b) Description of the Prior Art
Conventionally, single power systems are used in vehicles on land, at sea or in air. In recent years, owing to the consideration of energy saving and pollution control, dual power drive systems have attracted significant R&D investments, particularly in the areas of a hybrid drive system which integrating an internal combustion engine and a motor driven by electrical power from E.S.D. Various developed dual power drive systems are as follows:    1. A full-powered series-connected hybrid system: An engine is used to drive a generator which carries approximate power capacity to the engine, then under the control of drive control unit, the load is driven by a motor which also carries approximate power capacity to the engine, the motor is driven by the electricity generated by the generator; the drawback of the system is that, given various full load rates, efficiency differs excessively; and the power of engine does not support for direct load driving, Since the electricity from generator, under the control of drive control unit is transferred to the motor unit for load driving, therefore the power capacity of generator and motor unit must satisfying the demand of maximum power output. Therefore each of the engine, generator and motor unit must fulfill the demand of system maximum output power capacity, therefore the weight and cost is getting high, and the power of engine is unable to provide direct load driving while electrical units failed.    2. An energy-storing series-connected hybrid system: An engine is used to drive a generator, then, under the control of Drive Control Unit (D.C.U.), the load is driven by a motor that is, driven by the electricity generated by the generator; under light load conditions, part of the electricity generated by the generator is transferred into E.S.D. for storage, and the electricity stored in the E.S.D. is used to drive the motor to drive the load when the engine stops; and under heavy loading condition, the electrical energy from E.S.D. and generator jointly transferred to the motor unit for load driving. This architecture requires the installation of E.S.D, and the power from engine doesn't support directly load driving, therefore the power capacity of motor must satisfy the demand of system maximum output, and the capacity of generator shall be reduced with the installation of E.S.D, the power of engine is unable to offer load driving while electrical units failed.    3. A parallel-connected drive system: An engine is used to directly drive the load, whereas a generator is driven to charge E.S.D. at light load, so that once the engine stops, the electricity stored in the E.S.D. is used to drive the motor to drive the load; under heavy load conditions, the load is jointly driven by the engine as well as the motor driven by the electricity of the E.S.D.; the drawback of the system is that it is necessary to install E.S.D. of sufficient capacity, and high cost.